diff --git a/immutables/_map.c b/immutables/_map.c
index 7acf6c7e..5d961779 100644
--- a/immutables/_map.c
+++ b/immutables/_map.c
@@ -2810,9 +2810,23 @@ map_new_items_view(MapObject *o)
 /////////////////////////////////// _MapKeys_Type
 
 
+static int
+map_tp_contains(BaseMapObject *self, PyObject *key);
+
+static int
+_map_keys_tp_contains(MapView *self, PyObject *key)
+{
+	return map_tp_contains((BaseMapObject *)self->mv_obj, key);
+}
+
+static PySequenceMethods _MapKeys_as_sequence = {
+    .sq_contains = (objobjproc)_map_keys_tp_contains,
+};
+
 PyTypeObject _MapKeys_Type = {
     PyVarObject_HEAD_INIT(NULL, 0)
     "keys",
+    .tp_as_sequence = &_MapKeys_as_sequence,
     VIEW_TYPE_SHARED_SLOTS
 };
 
diff --git a/immutables/_protocols.py b/immutables/_protocols.py
index de87d230..49d8ee1e 100644
--- a/immutables/_protocols.py
+++ b/immutables/_protocols.py
@@ -32,6 +32,7 @@
 class MapKeys(Protocol[KT_co]):
     def __len__(self) -> int: ...
     def __iter__(self) -> Iterator[KT_co]: ...
+    def __contains__(self, __key: object) -> bool: ...
 
 
 class MapValues(Protocol[VT_co]):
diff --git a/tests/test_map.py b/tests/test_map.py
index 4640029d..4caef50a 100644
--- a/tests/test_map.py
+++ b/tests/test_map.py
@@ -1395,6 +1395,10 @@ def test_kwarg_named_col(self):
         self.assertEqual(dict(self.Map(a=0, col=1)), {"a": 0, "col": 1})
         self.assertEqual(dict(self.Map({"a": 0}, col=1)), {"a": 0, "col": 1})
 
+    def test_map_keys_contains(self):
+        m = self.Map(foo="bar")
+        self.assertTrue("foo" in m.keys())
+
 
 class PyMapTest(BaseMapTest, unittest.TestCase):